Question

The area of cross-section of the wider tube shown in figure is $800{\text{cm}}^2$. If a mass of $12\text{kg}$ is placed on the massless piston, the difference in heights $h$ in the level of water in the two tubes is

• A. $10\text{cm}$
• B. $6\text{cm}$
• C. $15\text{cm}$
• D. $2\text{cm}$

Answer 1

The correct option is C $15\text{cm}$

Given $m=12\text{kg},A=800{\text{cm}}^2$,
$\rho =1000{\text{kg/m}}^3$

From Pascals law,
$\frac{mg}{A}=P=\rho gh$ $(\because P=\rho gh)$
$\Rightarrow \frac{12\times 10}{800\times {10}^{-4}}=1000\times 10\times h$
$\Rightarrow h=\frac{12}{80}=0.15\text{m}=15\text{cm}$